include/linux/tracepoint.h

   1 #ifndef _LINUX_TRACEPOINT_H
   2 #define _LINUX_TRACEPOINT_H
   3
   4 /*
   5  * Kernel Tracepoint API.
   6  *
   7  * See Documentation/trace/tracepoints.txt.
   8  *
   9  * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  10  *
  11  * Heavily inspired from the Linux Kernel Markers.
  12  *
  13  * This file is released under the GPLv2.
  14  * See the file COPYING for more details.
  15  */
  16
  17 #include <linux/errno.h>
  18 #include <linux/types.h>
  19 #include <linux/rcupdate.h>
  20
  21 struct module;
  22 struct tracepoint;
  23
  24 struct tracepoint_func {
  25         void *func;
  26         void *data;
  27 };
  28
  29 struct tracepoint {
  30         const char *name;               /* Tracepoint name */
  31         int state;                      /* State. */
  32         void (*regfunc)(void);
  33         void (*unregfunc)(void);
  34         struct tracepoint_func *funcs;
  35 } __attribute__((aligned(32)));         /*
  36                                          * Aligned on 32 bytes because it is
  37                                          * globally visible and gcc happily
  38                                          * align these on the structure size.
  39                                          * Keep in sync with vmlinux.lds.h.
  40                                          */
  41
  42 /*
  43  * Connect a probe to a tracepoint.
  44  * Internal API, should not be used directly.
  45  */
  46 extern int tracepoint_probe_register(const char *name, void *probe, void *data);
  47
  48 /*
  49  * Disconnect a probe from a tracepoint.
  50  * Internal API, should not be used directly.
  51  */
  52 extern int
  53 tracepoint_probe_unregister(const char *name, void *probe, void *data);
  54
  55 extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
  56                                               void *data);
  57 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
  58                                                 void *data);
  59 extern void tracepoint_probe_update_all(void);
  60
  61 struct tracepoint_iter {
  62         struct module *module;
  63         struct tracepoint *tracepoint;
  64 };
  65
  66 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
  67 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
  68 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
  69 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
  70 extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
  71         struct tracepoint *begin, struct tracepoint *end);
  72
  73 /*
  74  * tracepoint_synchronize_unregister must be called between the last tracepoint
  75  * probe unregistration and the end of module exit to make sure there is no
  76  * caller executing a probe when it is freed.
  77  */
  78 static inline void tracepoint_synchronize_unregister(void)
  79 {
  80         synchronize_sched();
  81 }
  82
  83 #define PARAMS(args...) args
  84
  85 #ifdef CONFIG_TRACEPOINTS
  86 extern void tracepoint_update_probe_range(struct tracepoint *begin,
  87         struct tracepoint *end);
  88 #else
  89 static inline void tracepoint_update_probe_range(struct tracepoint *begin,
  90         struct tracepoint *end)
  91 { }
  92 #endif /* CONFIG_TRACEPOINTS */
  93
  94 #endif /* _LINUX_TRACEPOINT_H */
  95
  96 /*
  97  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  98  *  file ifdef protection.
  99  *  This is due to the way trace events work. If a file includes two
 100  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 101  *  will override the TRACE_EVENT and break the second include.
 102  */
 103
 104 #ifndef DECLARE_TRACE
 105
 106 #define TP_PROTO(args...)       args
 107 #define TP_ARGS(args...)        args
 108
 109 #ifdef CONFIG_TRACEPOINTS
 110
 111 /*
 112  * it_func[0] is never NULL because there is at least one element in the array
 113  * when the array itself is non NULL.
 114  *
 115  * Note, the proto and args passed in includes "__data" as the first parameter.
 116  * The reason for this is to handle the "void" prototype. If a tracepoint
 117  * has a "void" prototype, then it is invalid to declare a function
 118  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 119  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 120  */
 121 #define __DO_TRACE(tp, proto, args)                                     \
 122         do {                                                            \
 123                 struct tracepoint_func *it_func_ptr;                    \
 124                 void *it_func;                                          \
 125                 void *__data;                                           \
 126                                                                         \
 127                 rcu_read_lock_sched_notrace();                          \
 128                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
 129                 if (it_func_ptr) {                                      \
 130                         do {                                            \
 131                                 it_func = (it_func_ptr)->func;          \
 132                                 __data = (it_func_ptr)->data;           \
 133                                 ((void(*)(proto))(it_func))(args);      \
 134                         } while ((++it_func_ptr)->func);                \
 135                 }                                                       \
 136                 rcu_read_unlock_sched_notrace();                        \
 137         } while (0)
 138
 139 /*
 140  * Make sure the alignment of the structure in the __tracepoints section will
 141  * not add unwanted padding between the beginning of the section and the
 142  * structure. Force alignment to the same alignment as the section start.
 143  */
 144 #define __DECLARE_TRACE(name, proto, args, data_proto, data_args)       \
 145         extern struct tracepoint __tracepoint_##name;                   \
 146         static inline void trace_##name(proto)                          \
 147         {                                                               \
 148                 if (unlikely(__tracepoint_##name.state))                \
 149                         __DO_TRACE(&__tracepoint_##name,                \
 150                                 TP_PROTO(data_proto),                   \
 151                                 TP_ARGS(data_args));                    \
 152         }                                                               \
 153         static inline int                                               \
 154         register_trace_##name(void (*probe)(data_proto), void *data)    \
 155         {                                                               \
 156                 return tracepoint_probe_register(#name, (void *)probe,  \
 157                                                  data);                 \
 158         }                                                               \
 159         static inline int                                               \
 160         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 161         {                                                               \
 162                 return tracepoint_probe_unregister(#name, (void *)probe, \
 163                                                    data);               \
 164         }                                                               \
 165         static inline void                                              \
 166         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 167         {                                                               \
 168         }
 169
 170 #define DEFINE_TRACE_FN(name, reg, unreg)                               \
 171         static const char __tpstrtab_##name[]                           \
 172         __attribute__((section("__tracepoints_strings"))) = #name;      \
 173         struct tracepoint __tracepoint_##name                           \
 174         __attribute__((section("__tracepoints"), aligned(32))) =        \
 175                 { __tpstrtab_##name, 0, reg, unreg, NULL }
 176
 177 #define DEFINE_TRACE(name)                                              \
 178         DEFINE_TRACE_FN(name, NULL, NULL);
 179
 180 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 181         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 182 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 183         EXPORT_SYMBOL(__tracepoint_##name)
 184
 185 #else /* !CONFIG_TRACEPOINTS */
 186 #define __DECLARE_TRACE(name, proto, args, data_proto, data_args)       \
 187         static inline void trace_##name(proto)                          \
 188         { }                                                             \
 189         static inline int                                               \
 190         register_trace_##name(void (*probe)(data_proto),                \
 191                               void *data)                               \
 192         {                                                               \
 193                 return -ENOSYS;                                         \
 194         }                                                               \
 195         static inline int                                               \
 196         unregister_trace_##name(void (*probe)(data_proto),              \
 197                                 void *data)                             \
 198         {                                                               \
 199                 return -ENOSYS;                                         \
 200         }                                                               \
 201         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 202         {                                                               \
 203         }
 204
 205 #define DEFINE_TRACE_FN(name, reg, unreg)
 206 #define DEFINE_TRACE(name)
 207 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 208 #define EXPORT_TRACEPOINT_SYMBOL(name)
 209
 210 #endif /* CONFIG_TRACEPOINTS */
 211
 212 /*
 213  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 214  * (void). "void" is a special value in a function prototype and can
 215  * not be combined with other arguments. Since the DECLARE_TRACE()
 216  * macro adds a data element at the beginning of the prototype,
 217  * we need a way to differentiate "(void *data, proto)" from
 218  * "(void *data, void)". The second prototype is invalid.
 219  *
 220  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 221  * and "void *__data" as the callback prototype.
 222  *
 223  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 224  * "void *__data, proto" as the callback prototype.
 225  */
 226 #define DECLARE_TRACE_NOARGS(name)                                      \
 227                 __DECLARE_TRACE(name, void, , void *__data, __data)
 228
 229 #define DECLARE_TRACE(name, proto, args)                                \
 230                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),      \
 231                                 PARAMS(void *__data, proto),            \
 232                                 PARAMS(__data, args))
 233
 234 #endif /* DECLARE_TRACE */
 235
 236 #ifndef TRACE_EVENT
 237 /*
 238  * For use with the TRACE_EVENT macro:
 239  *
 240  * We define a tracepoint, its arguments, its printk format
 241  * and its 'fast binay record' layout.
 242  *
 243  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 244  * 'subsystem_event' notation is fine.
 245  *
 246  * Think about this whole construct as the
 247  * 'trace_sched_switch() function' from now on.
 248  *
 249  *
 250  *  TRACE_EVENT(sched_switch,
 251  *
 252  *      *
 253  *      * A function has a regular function arguments
 254  *      * prototype, declare it via TP_PROTO():
 255  *      *
 256  *
 257  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 258  *               struct task_struct *next),
 259  *
 260  *      *
 261  *      * Define the call signature of the 'function'.
 262  *      * (Design sidenote: we use this instead of a
 263  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 264  *      *
 265  *
 266  *      TP_ARGS(rq, prev, next),
 267  *
 268  *      *
 269  *      * Fast binary tracing: define the trace record via
 270  *      * TP_STRUCT__entry(). You can think about it like a
 271  *      * regular C structure local variable definition.
 272  *      *
 273  *      * This is how the trace record is structured and will
 274  *      * be saved into the ring buffer. These are the fields
 275  *      * that will be exposed to user-space in
 276  *      * /sys/kernel/debug/tracing/events/<*>/format.
 277  *      *
 278  *      * The declared 'local variable' is called '__entry'
 279  *      *
 280  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 281  *      *
 282  *      *       pid_t   prev_pid;
 283  *      *
 284  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 285  *      *
 286  *      *       char    prev_comm[TASK_COMM_LEN];
 287  *      *
 288  *
 289  *      TP_STRUCT__entry(
 290  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 291  *              __field(        pid_t,  prev_pid                        )
 292  *              __field(        int,    prev_prio                       )
 293  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 294  *              __field(        pid_t,  next_pid                        )
 295  *              __field(        int,    next_prio                       )
 296  *      ),
 297  *
 298  *      *
 299  *      * Assign the entry into the trace record, by embedding
 300  *      * a full C statement block into TP_fast_assign(). You
 301  *      * can refer to the trace record as '__entry' -
 302  *      * otherwise you can put arbitrary C code in here.
 303  *      *
 304  *      * Note: this C code will execute every time a trace event
 305  *      * happens, on an active tracepoint.
 306  *      *
 307  *
 308  *      TP_fast_assign(
 309  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 310  *              __entry->prev_pid       = prev->pid;
 311  *              __entry->prev_prio      = prev->prio;
 312  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 313  *              __entry->next_pid       = next->pid;
 314  *              __entry->next_prio      = next->prio;
 315  *      )
 316  *
 317  *      *
 318  *      * Formatted output of a trace record via TP_printk().
 319  *      * This is how the tracepoint will appear under ftrace
 320  *      * plugins that make use of this tracepoint.
 321  *      *
 322  *      * (raw-binary tracing wont actually perform this step.)
 323  *      *
 324  *
 325  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 326  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 327  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 328  *
 329  * );
 330  *
 331  * This macro construct is thus used for the regular printk format
 332  * tracing setup, it is used to construct a function pointer based
 333  * tracepoint callback (this is used by programmatic plugins and
 334  * can also by used by generic instrumentation like SystemTap), and
 335  * it is also used to expose a structured trace record in
 336  * /sys/kernel/debug/tracing/events/.
 337  *
 338  * A set of (un)registration functions can be passed to the variant
 339  * TRACE_EVENT_FN to perform any (un)registration work.
 340  */
 341
 342 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 343 #define DEFINE_EVENT(template, name, proto, args)               \
 344         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 345 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 346         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 347
 348 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 349         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 350 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 351                 assign, print, reg, unreg)                      \
 352         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 353
 354 #endif /* ifdef TRACE_EVENT (see note above) */